Regions

As with a large amount of commercial media, Nintendo games have different regional formats to discourage importing and to fit the corresponding region's video formats. These restrictions can be bypassed however with a variety of exploits, though at the user's own risk.

Older consoles which took cartridges simply had cartridges of different shapes. For example, Japanese Famicom cartridges were much smaller and had fewer pins than American NES carts, though convertors were made, not to mention older NES carts with convertor boards in them were used to adapt games.

Disc based media starting with the GameCube has been made with different region codes based on the country's video format and region, similar to DVD/Blu-Ray region codes. Circumvention of these regional barriers was slightly easier due to devices such as the Action Replay and Freeloader which simply disabled the lockout on the GameCubes made importation favorable to some. A region code disabler through the Homebrew Channel is available on the Wii for playing import games.

Handheld consoles are not dependent on the analogue TV standards' limitation (NTSC/PAL/SECAM), however the 3DS system software is designed to ignore a game if it does not correspond to the same region as the console (with the Chinese iQue 3DS being a special exception).

North America (NTSC-U)

* Note that these countries sometimes have games made exclusively for them, usually in French (NTSC-C) and Spanish (NTSC-M) respectively, these games however will still work in the other countries of this region without any modifications or lockout disabling devices.
As officially listed in the 3DS Region Settings, The U region works as the Americas/Asia region, specifically in these countries:

Anguilla

Antigua and Barbuda

Argentina

Aruba

Bahamas

Barbados

Belize

Bolivia

Brazil

British Virgin Islands

Canada

Cayman Islands

Chile

Colombia

Costa Rica

Dominica

Dominican Republic

Ecuador

El Salvador

French Guiana

Grenada

Guadeloupe

Guatemala

Guyana

Haiti

Honduras

Indonesia

Jamaica

Malaysia

Martinique

Mexico

Montserrat

Netherlands Antilles

Nicaragua

Panama

Paraguay

Peru

Philippines

Qatar

Saudi Arabia

Singapore

St. Kitts and Nevis

St. Lucia

St. Vicent and the Grenadines

Suriname

Thailand

Timor-Leste

Trinidad and Tobago

Turks and Caicos Islands

United Arab Emirates

United States

Uruguay

US Virgin Islands

Venezuela

Note that games of Japanese origin as well as systems are usually released in this region second, with American origin games being released in this secion first.